The invention relates to a method and to an arrangement for the excitation of the journalling winding and the drive winding systems in magnetically journalled electrical machines for the purpose of the impressing of angle independent forces and torques and to a corresponding electrical drive.
Magnetic journalling technology opens up fields of application in the construction of machines and apparatuses with extremely high demands on the speed of rotation range, the lifetime, the purity and the imperviousness of the drive system--thus substantially fields of application which cannot or can only with difficulty be realized using conventional journalling techniques. Various embodiments, such as for example high speed milling and grinding spindles, turbocompressors, vacuum pumps, or pumps for highly pure chemical or medical products are already being equipped with magnetic bearings.
A conventional magnetically journalled machine (FIG. 1) requires, in addition to a machine unit 1, two radial magnetic bearings 2 and 3, an axial magnetic bearing 4, two mechanical intercept bearings 5 and 6, as well as a total of ten power controllers 7, 8, 9 and 10 for the excitation of the motor and magnetic journalling loops. There are suggestions in the literature (FIG. 2) for integrating machines and radial magnetic bearings in a magnetic stator unit. Two separate winding systems 11 and 12 for drive and journalling force windings are introduced in multiple layers into grooves in a stator. Both winding systems have three loops and differ by one in the number of pole pairs. The coils are wound with fractional pitch and distributed over a plurality of grooves, through which an approximately sinusoidal flux linkage is achieved:
4-pole drive winding 11 (outer): first loop 13, second loop 14, third loop 15 PA1 two-pole bearing winding 12 (inner): first loop 16, second loop 17, third loop 18
The machine cross-sections illustrated in the figures are by way of example and are partly highly simplified and serve exclusively for the more precise explanation of the principle of operation.
Previously realized excitation concepts require sinusoidally distributed air gap flux densities and sinusoidal armature current layers. Distributed winding systems are thereby required (FIG. 2).